1. Field of the Invention
The present invention relates to a magnetic coupler having a thin film coil and magnetoresistive elements, and performing signal transmission in a contactless manner between a plurality of electric circuits isolated from one another.
2. Background Art
As a device for transmitting a signal in a contactless manner from one electric circuit to the other circuit among a plurality of electric circuits isolated from one another, a photo-coupler or a pulse transformer has been known in the past. However, significant aging deterioration occurs in the photo-coupler, including deterioration due to consumption of a light emitting diode (LED), or reduction in current transmission rate, in addition, significant delay in signal transmission. On the other hand, since the pulse transformer uses a winding coil, signal transmission delay is small therein. However, the pulse transformer has a problem of large size or weight, and a low operable temperature. In some coupler, the winding coil of the pulse transformer is substituted by a thin film coil. However, the coil does not efficiently receive a magnetic field, resulting in increase in power consumption.
Thus, a magnetic coupler has been developed for overcoming the difficulty (for example, refer to Published Japanese Translation of a PCT patent application No. 2003-526083, and Japanese Unexamined Patent Publication Nos. 2001-94174, 2001-135534, 2001-135535, 2001-135536, 2001-135537, 2001-196250, 2001-93763, and 62-40786). The magnetic coupler detects change in current, flowing through a signal line from one electric circuit system, in a contactless manner, and transmits an electric signal to the other electric circuit system. Therefore, the magnetic coupler is now noted as a device having an excellent operational reliability while having a simple configuration.